Community dial switching telephone system



Nov. 3, 1931. w. HATTON ET AL 1,829,798

COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM Filed March 8, 1930 4Sheets-Sheet 1 Q u |||||nn |n||||||| Q \Q\ g Q IIHI' INVENTORS w. HATTONC.DE VR/ENDT L EJROUSSEAU Nov. 3, 1931. w. HATTON ET AL 1,829,798

COMMUNITY DIAL SWITCHING TELEPHONE SYSTEM Filed March 8, 1930 4Sheets$heet 2 ti 5 m 2% a E VMHATTONv C. DE VR/ENDT EJROUSSEAU A TTORNEY Nov. 3, 1931. w. HATTON' ET AL COMMUNITY DIAL SWITCHING TELEPHONESYSTEM 4 Sheets-Sheet 4 Filed March 8, 1930 /NVENTORS \MHATTON C.DEVR/ENDT E.d. ROUSSEAU BY ATTOR /MEY Patented tam PATENT OFFICE WILLIAMHATTON, CHARLES DE VRIENDT, AND ERNEST JEAN BOUSSEAU, OF PARIS, FRANCE,ASSIGNORS T0 WESTERN ELECTRIC COMPANY, INCORPORATED, 013' NEW YORK, N.Y., A CORPORATION OF NEW YORK COMMUNITY DIAL SWITCHING TELEPHONE SYSTEMApplication filed March 8, 1930, Serial No. 434,215, and in GreatBritain November I, 1929.

This invention relates to dial switching telephone exchange systems andmore particularly to systems comprising small oflices known as satelliteor community offices. The object of the invention is to so arrange theapparatus of such community offices that subscribers whose linesterminate therein may by dialing directory numbers having a uniformnumber of digits either have access to subscribers lines which terminatein other oflices of the exchange system or have access to subscribers?lines which terminate locally with equal facility and in the case oflocal calls without the assistance of apparatus not local to thecommunity office in which the call originates.

In accordance with this invention two embodiments of which have beendisclosed herein by way of example, a subscriber whose line terminatesin the community office of the exchange area upon initiating a call atonce obtains connection over an idle trunk outgoing from the ofiice.This trunk may extend to a tandem district ofiice or to a central ofiiceof the exchange area. A typical exchange system of which the communityoflice may form a part is disclosed in our copending application SerialNo. 434,214, filed concurrently herewith. When the call so initiated hasbeen thus extended, the calling subscriber receives the customary dialtone and then proceeds to dial the digits of the wanted line number. Inall cases the subscriber dials a uniform number of digits, in theparticular system illustrated five digits. The first three digits dialeddetermine the destinaton of the call, that is, whether the call is foranother subscribers line terminating in the same community office or fora subscribers line terminating in some other office of the exchangesystem. If these digits indicate that the call is of a local character,then the outgoing trunk is released and the apparatus of the communityofiice is rendered efl'ect-ive to register the remaining two digitsdialed and to control the setting of local selector switches toterminate the call.

More particularly, referring to the first embodiment of the invention,the community ofiice is designed to have access to from 100 to 300lines, although it will be obvious that the principles of the inventionare applicable to such ofi'ices havingaccess to a larger number oflines. The ofiice is provided with a plurality of link circuits, eachsuch link terminating at one end in a line finder and at the other endin a plurality of branches each having a group selector. Thus, if theoffice is designed for access to 200 lines. each link will terminate intwo group selectors and if access is desired to 300 lines, each linkwill terminate in three group selectors. Of the lines to which thesegroup selectors have access, certain lines terminatin in one of thegroup selectors will be use for outgoing calls.

When a subscriber initiates a call by the removal of his receiver fromthe switchhook, all line finders of idle links having access to thecalling line are started in search of.

the calling line and when one of the line finders finds the callingline, it is seized and the finders of other links are stopped.Thereupon, that one of the group selectors of the link taken for usewhich has access to outgoing trunks is started in search of an idletrunk. When an idle trunk becomes associated with the link circuit, adiscriminating registering device which is common to the group of trunksis associated with the trunk taken for use in readiness for registeringthe first three digits to be dialed by the calling subscriber, and adialing tone is transmitted to the calling line. The calling subscriberthen proceeds to dial the first three digits of the wanted line number.If as will be assumed, these digits are indicative that the callingsubscriber desires a connection with another subscribers line whichterminates in the same ofiice, a discriminating signal is transmittedback to the link circuit and the registering device is released. Thissignal determines whether the wanted line may be reached over theterminal bank of the same group selector over which access was had tothe outgoing trunk, or whether it may be reached over one of the otherpar allelly connected group selectors, and renders marking registerswitches effective in the link circuit for recording the remaining twodi its of the line designation dialed by the calling subscriber. Inaccordance with the settings of the marking registers the group selectorwhich has been made effective by the discriminating signal is thereuponoperated to select the wanted line and to release the connection to theseized outgoing trunk.

The group selectors employed in connection with this embodiment-of theinvention have been illustrated as single motion hunting typestep-by-step switches, each having access to 100 sets of bank terminals.These selectors might, however, be of the wellknown clutch driven type.

Had the first three digits dialed indicated that the desired lineterminates in some other oflice of the exchange, then when the callingsubscriber dialed the last two digits, these digits would then have beentransmitted out over the trunk line for the purpose of con trollingselector switches at another" oflice rather than recorded on registersof the link circuit. In this case the common discriminating registeringdevice is effective to control apparatus in the trunk circuit for settinup a zone metering registration for metering the call in accordance withthe destination thereof. This metering feature, however, forms no partof the present invention but has been made the subject matter of our'copending application Serial No. 434,- 216, filed concurrently herein.

In the second embodiment of the invention the community oflice isdesigned to have access to a maximum of 100 lines and thus each linkcircuit is provided with two branches each terminating in a 50 ointstepby-step rotary group selector. If less than 50 lines terminate inthe ofiice, but one of these group selectors is necessary. As in themodification previously described, the initiation of a call causes theseizure of the calling line over the line finder of an idle linkcircuit, the seizure of an idle outgoing trunk and the associationtherewith of a discriminating. registering device.

If the first three digits dialed indicate that the call is of a localcharacter, a discriminating si nal is transmitted back to the linkcircuit in icative of that fact and the first of the two remainingdigits dialed by the calling subscriber is then registered upon amarking register'in the link circuit. As soon as this register steps offnormal, the group selector over which connection was made to theoutgoing trunk is started to advance and if the marking registerindicates that the wanted line is located in a tens group to which suchgroup selector has access, the group selector will advance to suchmarked tens group. Thelast digit dialed. by the calling subscriber willthen set that group selector in a units selection movement to theterminal of the wanted line. If, however, the community ofiice has morethan 50 lines terminating therein and the link circuit also terminatesin a further group selector and the tens di it recorded indicates thatthe wanted line is ocated in a tens group to which such other groupselector has access,

hunting movement to the group marked by the marking register. The unitsdigit dialed by the calling subscriber is then employed to set suchgroup selector in a units selection movement upon the terminals of thewanted line.

Provision is also made for releasing an established connection to acalled subscribers line through the o eration of a thermostatic relay ifthe calling subscriber fails to restore his receiver within apredetermined interval following the restoration of the calledsubscribers receiver.

Referring to the drawings, Fig. 1 shows at the left a subscribers line,one of the link circuits of the community oflice terminating at one endin a line finder and at the other end in a plurality of parallellyconnected group selectors, tens and units marking switches forcontrolling the setting of the group selectors and at the right oneoutgoin trunk circuit and a subscribers line terminating in the bank ofone of the group selectors.

Fig. 2 shows the apparatus associated with the outgoing end of the trunkcircuit and in the lower right portion of the fi ure a message registerimpulsing switch or controlling the calling line message register ofFig. 1 in accordance with the zone of the exchange into which aconnection is extended. Fig. 3 shows a discriminating registering devicefor recording and translating the first three digits dialed by a callingsubscriber together with a trunk huntingswitch, shown in the upperportion of the figure, whereb the registering device may be associatedwith any one of -a group of trunk circuits.

ig. 4 shows a modification of the link circuit shown in Fig. 1.

For a com lete disclosure ofthe invention 2 shoul be placed at the rightof Fig. 1

F1 and Fig. 3 should be placed beneath Fig. 2.

The invention when considered in connection with the modification shownin Fi 4 may be illustrated by placing Fig. 4 in pace of the link circuitshown in Fig. 1.

All of the switches disclosed are of the single motion step-by-steptype. The finders and 400 of Figs. 1 and 4 are of the type having nonormal position and each is equipped with two sets of wipers placed onthe switch shaft 180 apart. The group selectors 110, 120 and 130 of Fig.1 are of the same general type as the line finders and each has accessto one hundred sets of bank terminals. The group selector 110 has accessto a group of five outgoing trunks and to 90 subscribers lines and theother two group selectors 120, and 130, the wipers of selector 130, notbeing illustrated, each have access to one hundred subscribers lines.The marking switches 140, 150 and 430, the registers 310 and 320 and themessage register impulsing switch 200 are all minor type switches. Thetranslator switch 330 of Fig. 3 has access to fifty sets of bankterminals, the terminals of the upper four levels being cross-connected,as may be desired, to the cross-connecting frame 340 for controllingmetering and the selection of a proper group switch of Fig. 1 forestablishing local connections. The trunk hunting switch 300 which hasno normal position has access to the group of trunk circuits, one ofwhich is disclosed in Fig. 2. The group selector switches 410 and 420 ofFig. 4 are similar to the selector switches of Fig. 1, but have accessrespectively to but fifty sets of line terminals.

' For a better understanding of the invention reference may be had tothe following 5 description in which the progress of a call from thecalling line 101 over the circuits of Figs. 1 to 3 inclusive, will firstbe described in detail. \Vhen the calling subscriber removes hisreceiver from the switchhook a circuit is established from battery,through the winding 'of line relay 102, the upper back contact ofcut-off relay 103, over the loop of the calling line to ground at thelower contact of relay 103. Relay 102.upon operating establishes anobvious circuit for the common group relay 104 which in turn establishesa circuit for the common line finder start relay 105. Relay 105 at itsfront contacts closes start circuits for the stepping magnets of allidle line finders having access to the group of lines in which thecalling line is located. It will be assumed that the line finder 100 isthat one of these line finders which is to be used in establishing theconnection. The circuit for starting this line finder may be traced frombattery, through the magnet winding and interrupter contacts of steppingmagnet 106, contacts of relay 105, contacts of test jack 107, backcontact of relay 108 to ground at the upper normal contacts of relay109.

In response to the operation of magnet 106 the wipers of the line finderare advanced until the test wiper 111 engages the test terminal of thecalling line. Then a circuit is established from ground, through thelower winding of relay 108, the normal contact of thermostatic relay112, contacts of jack 107. wiper 111 to battery at the front contact ofrelay 102. Relay 108 upon energizing closes an obvious circuit for relay113 and opens at its back contact the circuit of stepping magnet 106.\Vith relay 113 operated, ground is connected over the lower contact ofrelay 113 and the upper winding of relay 108 to .test wiper 111 toprevent the seizure of the is found, relay 117 operates in a circuit extending from ground at the upper normal contact of relay 118, wiper 119of markin switch 140 and its normal terminal, strapped terminals withwhich wi-per 121 of the group selector engages, winding of relay 117,inner upper front contact of relay 113, wiper 122,

conductor 201 to battery through the winding of relay 202. Relay 202also operates in this circuit and performs a function which will bedescribed later.

Relay 117 upon operating, opens the circuit of magnet 114 to arrest theoperation of the group selector 110 and establishes over its frontcontact and a contact of relay 113 a circuit for relay 123. At its innerlower front contact relay 123 applies direct ground through the windingof relay 117 over wiper 122 to conductor 201 to mark the selected trunkbusy and closes an obvious circuit for relay 124. Relay 124 uponoperating establishes a circuit from ground through the winding of relay109, over wiper 125 of line finder 100 to battery through the callingline cut-off relay 103. Relay 103 disconnects the line relay 102 whichin turn releases relay 108 and if there are at the time no other linescalling in the group, releases common relays 10. and 105 therebyarresting the operation of an other idle line finders that may have beenstarted. After the release of relay 108, relay 113 is locked over itsinner lower front contact, the back contact of relay 126 to ground atthe upper front contact of relay 109.

Relay 202 of the link circuit which operated in series with test relay117 upon operating establishes an obvious circuit for relay 203. Withrelay 109 operated a circuit is established from ground, through theupper winding of relay 204, wiper 127 ofselector 110, upper alternatecontacts of relay 123, lower front contact of relay 109, wiper 128, overthe calling line, back over wiper 129, the inner upper contact of relay109, the inner upper front contact of relay 123, wiper 131 to batterythrough the lower winding of relay 204. Re ay 204 operates in thiscircuit and closes an obvious circuit for slow to release relay 205which operates in turn and causes the operation of relay 206. An impulserepeating circuit is now extended over the outgoing conductors 207 and208 of the trunk circuit for repeating impulses to the oflice to whichthe community oflice is subsidiary, this circuit extending fromconductor 207 over 206 at its inner upper contact connects busypotential from the upperback contact of relay 215 over the normalcontacts of thermostatic relay 217, resistance 218, contacts of relay206 to conductor 201 in parallel with relay 202 for holding relay 117 ofthe district link circuit operated. At is innermost lower front contactrelay 206 connects marking potential over the lower back contact ofrelay 211, the inner lower front contact of relay 206 to test terminals301 of all trunk finders similar to trunk finder 300 of Fig. 3 and inparallel to ground through start relay 302. Relay 302 operates closingan obvious circuit for relay 303 which in turn establishes operatingcircuits for the stepping magnets of all idle trunk finders individualtoidle registering devices. One of these registering devices is shown inFig. 3 and it will be assumed that this registering deviceis idle andbecomes connected with the trunk of Fig. 2. The operatin g circuit oftrunk finder 300 of this register-. ing device may be traced frombattery, through the winding and interrupter contacts of stepping magnet304, a contact of relay 303 to'ground at the back contact of relay 305.When the calling trunk is found and test wiper 306 of trunk finder 300engages terminal 301., the circuit previously traced to terminal 301 isextended over wiper 306, the upper winding of relay 305 to ground at thenormally closed contacts of the oif-normal springs 354 of translatorswitch 330. Relay 305 thereupon operates opening the circuit of magnet304 and closes an obvious circuit for relay 307 which at its lower frontcontact connects the low resistance winding of relay 305 into circuitwith wiper 306 to busy the trunk circuit to other trunk finder switches.

Relay 307 also closes a circuit in parallel through the windings ofrelays 210 and 211 over wiper 308, the innermost upper front contact ofrelay 307, resistance 355, normal terminal and wiper 309 of register310, normal terminal and wiper 311 of register 320 to ground at the backcontact of relay 312. Relay 210 operates to close the outgoing trunkcircuit so that the subscriber may receive a dial tone incoming over thetrunk circuit. Relay 211 being marginal does not, however, operate atthis time because of the resistance in its operating circuit. Thecontinuity of the loop circuit over the outgoing trunk circuit is not,however, broken by the operation of relay 210 since it is maintainedthrough the winding of supervisory relay 212.

When the calling subscriber receives dialing tone incoming over trunkconductors 207 and 208 and transmittedover front contacts of relay 210,he proceeds to dial the digits of the wanted line number. It will beasthe winding of relay 3 12 in a circuit extending from ground at thelower back contact of relay 204, the intermediate lower front contact ofrelay 206, wiper 313, the upper inter mediate front contact of relay307, windin of relay 312, inner upper back. contact 0 relay 314, backcontact of relay 315 to battery through the winding of stepping magnet316 of the register 310. Relay 312 operates in this circu1t and beingslow to release remains energized during the transmission of the seriesof impulses and at its back contact opens the previously traced circuitof relay 210 which thereupon deenergizes and shunts the winding of relay212 from the outgoing trunk dialing loop'for permitting the betterrepetition of impulses over the outgoing trunk circuit. At its uppercontacts relay 204 repeats impulses over the outgoing trunk circuit. As,however, this invention is not concerned with the repetition of impulsesover the outgoing trunk no further reference will be made theretoherein. The first digit dialed thus sets the register 310 into itsseventh position and upon the termination or the impulses relay 312releases and closes a circuit for relay 315 extending from battery,

winding of rela 315, off-normal terminals and wiper 309 o register 310,normal terminal and wiper 311 of register 320 to ground at the backcontact of relay 312. Relay 315 energizes and locks over its lowercontact to ground applied to conductor 353 at the upper front contact ofrelay 307, and switches the impulsing circuit previously traced from thewinding of magnet 316 of register 310 over the upper back contact ofrelay 322 to the winding of magnet 317 of register 320.

The second digit four dialed by the calling subscriber now sets theregister 320 to its fourth terminal position. Immediately the seconddigit register 320 moves 01f normal, the rotation of translator switch330 is started by a circuit extending from battery, through the windingand interrupter con tacts of magnet 318, the olf-normal terminals andwiper 319, lower back contact of relay 321, lower back contact of relay322, to

ground on conductor 353. The terminals in the lowermost bank of register320 are connected in pairs 1, 2; 3, 4; etc., and are connected byjumpers to terminals 1, 11, 21, etc., in the marking level of thetranslator switch 330. The translator switch hunts for the markedterminal under the control of test relay 321, but if the first terminalis marked the switch does not move since relay 321 will operateimmediately when register 320 leaves normal over a circuit extendingfrom battery, wiper 323, No. 1 terminal 324 and wiper 325 of translatorswitch 330, upper normal contacts of relay 314 to ground through thewinding of relay 321. When the marked terminal 326 is found, relay 321operates over the circuit just traced, opening the circuit of steppingmagnet 318. Vhen the relay 312 again deenergizes upon the termination ofthe second series of impulses, with relay 321 operated a circuit isclosed for relay 322 extending from battery, winding of relay 322, frontcontact of relay 321, off-normal terminals and wiper 311 of register 320to ground at the back contact of relay 312. Relay 322 operates and locksto ground on conductor 353.

In response to the dialing of the third digit one, an impulse isrepeated by the impulsing relay 204 as before traced through the windingof relay 312, thence over the upper front contact of relay 315, theupper front contact of relay 322 to battery from the Winding of steppingmagnet 318. It was assumed that the third digit was one and thereforethe translator wipers are advanced one step further. As'soon as wiper325 leaves terminal 326, the circuit of relay 321 is opened. When relay312 again deenergizes upon the termination of the third digit series ofimpulses a circuit is established for relay 314 extending from batterythrough the winding of relay 314, inner lower front contact of relay322, back contact of relay 321, thence as traced to ground at the backcontact of relay 312. Relay 314 upon operating locks over its innerlower front contact to ground on conductor 353.

The terminals of the four upper levels of translator switch 330aremultipled in accordance with the size of the various oflices of theexchange and are jumpered to the points 336, 337 and 338 in accordancewlth the distance between the originating office and the other offices.It will be noted that the even numbered terminals of the bank associatedwith wiper 341 are multipled to the wiper switching relay 333 and thatas the second digit dialed was four, or of even value, relay 333 isoperated over wiper 341 and the inner upper front contact of relay Inaddition the sixth and seventh terminals in the bank of register 310 towhich wiper 342 has access are connected to the armatures of relay 333and in accordance with the energized or deenergized condition of thisrelay, are connected to either wipers 343 and 344, or 345 and 346 of thetranslator switch. Since it has been assumed that the register 310 wasset into its seventh terminal position and that relay 333 is operated,wiper 344 only is connected in a circuit over wiper 342, theintermediate lower front contact of relay 314 to ground on conductor353. Since also the translator has been adtit the inner upper frontContact of relay 307,

wiper 308 to battery through the windings of relays 210 and 211 therebycausing the operation of these relays. It having been assumed thatconnection is to be made with the line of a local subscriber which maybe reached over the wipers of group selector 110, no cross-connection ismade between terminal 357 and the cross-connection points 336, 337 and338 and therefore relays 213, 214 and 339 are not operated at this timeand no discriminating signal is therefore sent to the district linkcircuit over conductor 216 upon the operation of relay 215.

At its upper back contact relay 215 disconnects battery potential fromconductor 201 thereby releasing relay 117 in the link circuit in turnreleasing relay 123. The release of relay 123 in turn opens the circuitof relay 204 in the trunk circuit releasing relays 205 and 206 of thetrunk circuit and relays 305 and 307 of the register circuit. Therelease of relay 307 removes holding ground from conductor 353 therebyreleasing operated relays 314, 315, 322 and 332 and in turn releasingrelay 333 and 215. A circuit is now established for restoring theregister 320 extending from battery, through the winding and interruptercontacts of magnet 317, off-normal terminals and wiper 348 of register320, back contact of relay 307 to ground at the off-normal contacts 354of translator switch 330. When the register 320 reaches normal theoperating circuit for magnet 316 of register 310 is established frombattery, through the winding and interrupter contacts of magnet 316,wiper 349 and the off-normal terminals of the bank with which itcooperates, the normal terminal and wiper 348 of register 320, thence toground as traced to oil-normal contacts 354. When the register 310reaches normal the operating circuit of magnet 318 of translator switch330 is established from battery through the winding and interruptercontacts of magnet 318, the normal terminal and wiper 349 of register310, thence as traced to ground. Its restoring circuit is opened whenthe translator reaches normal and opens contacts 354. Trunk finder 300has no normal position and remains in contact with the terminals of thetrunk circuit last used. All apparatus of the trunk circuit of Fig. 2

and register of Fig. 3 isnow in normal condition.

At the district link circuit of Fig. l u on the release of relay 123 thewindings of re ay 126 are connected to the calling line loop over thecontacts of relay 109 before slow to release relay 124 has had time torelease following the release of relay 123, and a new holding circuitfor relay 124 is therefore established over'the upper front contact ofrelay 126 to ground over conductor 138 and the upper front contact ofrelay 109. When the calling subscriber now dials the tens digit whichwas assumed to be two, relay 126 releases for each impulse andestablishes a circuit for the tens marking switch magnet 132 whichextends from battery, through the.

winding of magnet 132, lower back contact of relay 133, winding of relay134, back contact of rela 113, which released upon the operation 0 relay126, back contact of relay 126 to ground on conductor 138. Slow torelease relay 134 operates in series with magnet 132 and remainsoperated until the tens Series of impulses terminates.

As soon as the marking switch 140 leaves normal the group selector 110starts hunting by reason of a circuit for its stepping magnet extendingfrom battery, through the winding of magnet 114, lower back contacts ofrela s 115and 116, off-normal terminals and wiper 135 of marking switch140 to ground at the back contact of relay 117. When the impulses of thetens digit have been comp'letel transmitted relay 134 releases and acircuit 1s established in parallel from battery, through the upperwinding of relay 136 and the winding of relay 133, over the lower normalcontacts of relay 118, wiper 137 and off-normal terminals of switch 140,back contact of relay 134, inner upper back contact of relay 118 tooff-normal ground on con ductor 138. Relay 133 looks itself operatedover its inner lower front contact to ground at the back contact ofrelay 142 and changes the impulsing circuit controlled by relay 126 fromthe winding of magnet 132 to the winding of magnet 139 of units markingswitch 150 which is now set in response to the dialing of the unitsdigit five. Relay 136 locks over its locking contact and lower windingand back contact of relay 145 to off-normal ground on conductor 138..

When the group selector 110 reaches the terminal 170 of its markinglevel marked by the setting of the tens marking switch 140, the markingswitch having been positioned in position 2, a circuit is establishedfor relay 117 which may be traced from battery, offnormal terminals andwiper 141 of marking 1 switch 140, winding of relay 117, wiper 121,

terminal 17 0, wiper 119 to ground at the upper back contact of relay118. Relay 117 now opens the circuit of the stepping magnet 114 of thegroup selector and closes the circuit of relay 118 extending frombattery, through the upper winding of relay 118, the upper intermediatefront contact of relay 133 to ground at the front contact of'relay 117.Relay 118 then looks over its lower winding and inner lower frontcontact to off-normal ground on conductor 138 and switches markingground at its upper contacts from wiper 119 of marking switch 140 to thewiper 143 of the units of mark ng switch 150. Until the marking switch150 moves beyond its first terminal position relay 117 is held op eratedfrom ground over wiper 143, wiper 119, terminal'170, wiper 121, thenceas traced through the winding of relay 117 to battery at wiper 141 sothat if the units digit is one the group selector does not move further.

It has been assumed, however, that the units digit dialed was five andtherefore when marking switch 150 moves beyond position 1, relay 117releases and closes the circuit of magnet 114 of the group selector toad- Vance it one step whereupon relay 117 again operates. In this'mannerthe group selector follows the setting of the units marking switch stepby step. When the units series of impulses-ceases, relay 134 againdeenergiyes and establishes a circuit for relay 142 extending frombattery, through the winding of relay 142, off-normal terminals andwiper 144, of the units marking switch .150, lower front contact ofrelay 118, off-normal terminals and wiper 1.37 of tens marking switch140,

back contact of relay 134, inner upper front contact of relay 118 toground at the front contact of relay 117. Relay 142 opens the lockingcircuit of relay 133 and during the releasing time of slow to releaserelay 133 a circuit is established for the test relay 146 extending fromground at the upper front contact of relay 142, the inner upper frontcontact ofrelay 133, upper winding of relay 146 to the test wiper 122,.thence over the test terminal of the wanted line 160 to battery throughthe cut-off relay 148. If the line is idle, relays 148 and 146 operateand relay 146 locks over its lower winding and intermediate lowercontact to off-normal ground on conductor 138. At its upper frontcontacts relay 146 switches through the talking connection from wipers127 and 131 through condensers 149 and 151 back contacts of relay 123and front contacts of relay 109 to wipers 128 and 129. At its innerlower front contact the test wiper 122 is connected to test wiper 125 sothat the cut-off relays 103 and 148 of the calling and called lines areconnected in parallel through the winding of relay 109 to ground at thefront contact of relay 124.

Ringing current is now applied to the calling line from the ringingcurrent source 152 through thewinding of ringing cut-olf relay 145,'tl1eupper front contact of relay 136, the inner upper front contact of relay146, wiper 131, thence over the called line 160 and through thesubstation bell returning over wiper 127, the upper front contact ofrelay 146, the inner upper front contact of relay 136 to ground at thelower front contact of relay 142. A ringing tone is transmitted to thecalling line over the upper back contact of relay 133, condensers 153and 151, thence as traced over the calling line. When the calledsubscriber answers, relay 145 energizes releasing relay 136 todisconnect the source of ringing current and ringing tone and to connectthe windings of the back bridge relay 154 to the conductors of thecalled line. Relay 154 now operates in a circuit extending from battery,through its lower winding, upper back contact of relay 136, inner upperfront contact of relay 146, wiper 131, thence over the called line,returning over wiper 127, the upper front contact of relay 146, toground throughthe upper winding of relay 154.

A circuit is now effective for operating the calling line messageregister 155 which may be traced from ground, through the Winding ofmessage register magnet 155, wiper 156, lower front contact of relay 146to battery through the inner lower back contact of relay 1-36. Upon thetermination of the conversation, when the calling subscriber restoreshis receiver, relay 126 releases followed by the release inturn ofrelays 124 and 109. When relay 109 releases it removes holding groundfrom conductor 138 thereby releasing all other operated relays of thelink circuit and releasing the cut-off relays 103 and 148 of the callingand called lines. lVith relay 124 deenergized, a restoring circuit isestablished for marking switch 140 extending from battery, through thewinding and interrupter contacts of magnet 132, off-normal terminals andwiper 157, to ground at the back contact of relay 124. When switch 140reaches normal the winding of magnet 132 is disconnected from wiper 157and ground from wiper 157 is extended over wiper 158 and theoff-normalterminals of its bank through the interrupter contacts andmagnet winding 139 of marking switch 150. Switch 150 is thereby restoredto normal in which position the circuit of magnet 139 is opened. Groupselector 110 returns to normal upon the seizure of the link circuit forthe next call.

If the calling subscriber holds the line for thirtyseconds after thecalled subscriber restores his receiver and releases back bridge relay154, a circuit becomes established for the thermostatic relay 112extending from battery, through the winding of relay 112, the lowerfront contact of relay 126, the upper back contact of relay 154, theinner upper back contact of relay 136 to ground at the lower frontcontact of relay 142 which is effective to connect battery over theupper contacts of jack 107, wiper 111, the back contact of line relay102 to ground through the upper winding of fault relay 159. Relay 159upon operating locks over its lower winding in a circuit extending overthe calling line to round at the upper contact of relay 159, and at itsinner upper front contact connects a shunt over wiper 125 therebycausing relay 109 to deenergize and release the connection. The callingline cut-off relay 103 is also operated by relay 159 thereby preventingthe line relay 102 from reoperating and an alarm circuit is closed overthe lower contact of relay 159 to apprise the attendant that the callingsubscriber has not restored his receiver as he should. As soon as thecalling subscriber hangs up, relay 159 releases and restores the callingline to its normal condition.

In the foregoing description it was assumed that the wanted local linewas reached over the wipers of the group selector 110. It will now beassumed that the calling subscriber dialed the number 73125 of a localline terminating in the bank of group selector 120. The circuitsfunction in the manner previously described up to the point where thefirst three digits have been registered in the register translator.Since the second digit registered by the register 320 is now assumed to,be three, the translator brush 346 is set upon terminal 350 and uponthe energization of relay 314, following the termination of the thirdimpulse series, the circuits of relays 332 and 215 are again closed andin addition relay 213 is operated in a circuit extending from ground onwiper 346, terminal 350, cross-connection point 336, the inner upperfront contact of relay 332, wiper 334 to battery through the winding ofrelay 213. lVith relay 332 operated, the circuit of relay 211 isestablished as previously described, locking itself and relays 213 and215 to off-normal ground on conductor 221.

lVith relay 215 operated the holding circuit of relay 117 is opened,releasing this relay and in turn releasing relay 123. A circuit is nowclosed from ground, through re sistance 219, over front contacts ofrelays 213 and 215, conductor 216, thence over wiper 161, the lower backcontact of relay 123 to battery through the windings of relays 115 and116. Relay 116 being marginal, only relay 115 operates in this circuit,locking over its inner upper front contact and the upper back contact ofrelay 116 to ground on conductor 138. At its lower back contact relay115 disconnects the winding of stepping magnet 114 of group selector 110and at its lower front contact connects the winding of stepping magnet162 of group selector 120 in a circuit extending over the lower backcontact of relay 116 to the off-normal terminals associated with wiper135 of the tens marking switch 140 preparatory to advancing the wipersof the group selector 120 as soon as the tens marking switch operates inresponse to the dialing of the tens digit. Relay 115 also establishes acircuit extending from ground at its upper front contact, over theoff-normal contacts 168 of selector 110 to battery through theinterrupter contacts and magnet winding of magnet 114 whereby the groupselector 110 is restored to normal releasing the selected trunk circuit.All appa-- ratus associated with the trunk circuit is then restored inthe manner previously described.

In response to the dialing of the tens and units digits the markingswitches 140 and 150 are set as previously described and the groupselector 120 is started in its group or. tens selection movement as soonas the wiper 135 leaves normal. \Vhen the selector wipers reach the setof terminalsv marked by the tens marking switch 140, the wiper 164 willbe in engagement with terminal 165 and the further movement of the groupselector will be stopped by the operation of relay 117. The unitsselection movement of the group selector is then controlled by thesetting of the marking switch 150 in the same manner as previouslydescribed in connection with the marking switches 140 and 150 to normal.

When the marking switches have both reached their normal positions arestoring circuit forgroup selector 120 is then established frombattery, through the winding and interrupter contacts of magnet 162,off-normal contacts 166, normal terminal and wiper 158 of switch 150,normal terminal and wiper 157 of wiper 140 to ground at the back contactof relay 124 thereby restoring the group selector 120 to normal. 1

Had the calling subscriber dialed the number 64125 of a local subscriberwhose line terminates in the bank of groupselector 130 the circuitswould have functioned as previously described up to the point where thetranslator 330 was set in response to the dialing of the third digitexcept that the register 310 would have been set into position sixrather than position seven and register 320 would have been set intoposition four. In this case following the termination of the dialing ofthe third digit and the operation of relay 314, with relay 333 operated,the wiper 343 of the translator is made effective and since wiper 343 isnow standing on terminal 351 a circuit is established for relay 332which in turn operates relay 215. Terminal 351 is also connected by ajumper to cross-connection point 337 so that upon the operation of relay332 the operating circuit of relay 332 is extended over the lowercontact of relay 332, brush 335 to battery through the winding of relay214. Relays 214 and 215 upon operating both lock over a front contact ofrelay 211 to off-normal ground on conductor 221.

With relay 215 operated the holding circuit of relay 117 is openedreleasing relay 117 and in turn releasing relay 123. A circuit is nowclosed from "ground at the inner lower front contact of relay 214, thelower front contact of relay 215 to conductor 216, thence over wiper161, the lower back contact of relay-123 to battery through the windingsof relays 115 and 116. Both of these relays operate in this circuitlocking over the upper front contacts of relay 116 to ground onconductor 138. At its lower back contact relay 115 disconnects thewinding of stepping magnet 114 of group selector 110 and at its lowerfront contact relay 116 connects the winding of stepping magnet 167 ofgroup selector 130 in a circuit extending over the lower front contactof relay 116 to the off-normal terminals associated with wiper 135 ofthe tens marking switch 140 preparatory to advancing the wipers of groupselector 130 as soon as the tens marking switch operates in response tothe dialing of the tens digit. Relay 115 also establishes a circuitextending from ground at its upper front contact over the off-normalcontacts 168 of the selector 110 to battery through the interruptercontacts and ma net winding of magnet 114 whereby group se ector 110 isrestored to normal releasing the selected trunk circuit. All apparatusassociated with the trunk circuit is then restored in the mannerpreviousl described. From this point the circuits 0 Fig. 1 function inthe manner previously described except that the marking switches 140 and150 mark terminals in the marking level, not shown, of group selector130 to set this group selector upon the terminal of the wanted line. I

In the foregoing description it has been assumed thatlthe first threedigits dialed by the calling subscriber indicated that a connection wasdesired with a local subscribers line. If, however, these digits had forexample been 742, indicative of a connection to'be com leted beyond thedistrict or community o ce, then following the completion of dialing thethird digit and the operation of relay 314, no immediate circuit wouldbe completed for relay 332 as the translator bank terminal 352 uponwhich the wiper 344 is then resting is not cross-connected tocrossconnection point 349. Conse uently relav 215 is not at this timeoperated to cause the release of the trunk circuit and the remaining twodigits of the line number dialed bv the calling subscriber are received'in the register translator circuit.

- No record of the denomination of the fourth and fifth digits dialed istaken in the register circuit, but pairs of relays 327, 328

and 329, 331 are energized at the beginning and end of the tens andunits di 't series respectively under the control 0 relay 312. 'Thus, atthe beginning of the fourth or tens digit a circuit is established frombattery,

through the Winding of relay 327, back contact of relay 328, lower frontcontact of relay 314 to ground at the front contact of relay 312. Relay327 thus operates lockmg through the winding of relay 328 and over itsown contact to ground on conductor. 353 but relay 328 being shunted doesnot operate. When relay 312 deenergizes, however, at the end of the tensdigit series, relay 328 operates. At the beginning of the fifth or unitsdigit series relay 312 again operates and establishes a circuit forrelay 329 extending from battery through the winding of this relay,front contact of relay 328,,thence as traced to ground at the frontcontact of relay 312. Relay 329 operates and locks in series with relay331 over its own front contact to ground on conductor 353, but relay 331being shunted at the front contact of relay 312 does not energize inthis locking circuit. When, however, relay 312 deenergizes at the end ofthe units digit series relay 331 operates and establishes a circuit forrelay 332 extending from battery through the Winding of relay 332, thefront contact of relay 331 to ground on conductor 353.

Metering control relays 213 and 214 are now connected over wipers 334and 335 of the trunk finder 300 and front contacts of relay 332 tocross-connecting points 336 and 337 of cross-connecting rack 340. Afurther point 338 is connected b relay 332 to the "winding of relay 339.t will-be assumed "that for the particular setting of the translatorswitch in response to the digits 742 the translator bank terminal 352 isjumpered to the point 338 and that therefore following the operation ofrelay 332, a circuit is established for relay 339 extending through thewinding of relay 339, over the inner lower front contact of relay 332,terminal 352,

- wiper 344, lower front contact of relay 333 which was operated withregister 320 in position 4, the seventh terminal and wiper '342 ofregister 310, the intermediate lower front contact of relay 314 toground on conductor 353. Relay 339 upon operating completes the circuitsof bothrelays 213 and 214. Had

the first three digits dialed been, for example, 732 or 642, then uponthe operation of relay 332 the relay 339 would not be operated, buteither relay 213 or relay 214 would be operated singly. Thus dependentupon the first digits dialed three metering conditionsmay be establishedby the operation of both or either of relays 213 and 214.

In addition to selectively operating the meter control relays 213 and214, relay 332 connects direct groundover its upper contact, the innerupper front contact of relay 307, wiper 308 to battery through thewindstrumental in setting up a connection at a distant oilice to theline of a desired subscriber. When such subscriber answers the circuitextending over conductor 208 is momentarily opened thereby releasingrelay 212. Relay 212 upon releasing now closes a circuit for relay 220extending from battery, through the winding of relay 220, upper frontcontact of relay 211, upper back contact of relay 212 to ground onconductor 221. Relay 220 looks to conductor 221 and as soon as relay 212again energizes, establishes a circuit for relay 209 extending over theupper front contact of relay 220, the front contact of relay 212 toground on conductor 221. Relay 209 also looks to conductor 221 andestablishes an obvious circuit for the time switch 222 which receives animpulse every two seconds from the master clock circuit.

A circuit is also established from battery, through the winding ofmetering switch magnet 223, wiper 224 and the normal terminal upon whichit is resting, contact 225 of the time switch 222 to ground at theintermediate upper front contact of relay 209 for advancing the switch200 one step off normal, from which position it rotates through a singlecycle under the control of interrupter 226. As soon as the time switch222 leaves normal it opens contact 225 so that when the metering switch200 reaches normal its advance is arrested. With relays 213 and 214 bothoperated as previously described, when the wiper 227 of the meterinswitch 200 passes over the first, third and fth terminals of its bankthree metering impulses are transmitted over a circuit which extendsfrom metering battery, through resistance 228, the upper front contactof relay 214, terminals and wiper 227 of switch 200, the lower backcontact of relay 215, conductor 216, wiper 161, the lower front contactof relay 123, wiper 156 to ground through the message register magnet155. These impulses are then followed by two further impulsestransmitted from battery, through resistance 228, the lower frontcontact of relay 213, the seventh and ninth terminals and wiper 227 ofswitch 200, thence as traced through the winding of message registermagnet 155.

After three minutes, timeswitch 222 again closes contact 225 and themetering switch 200 again completes a cycle transmitting five additionalmetering impulses. This sequence circuiting ground to the winding ofrelay 117 in the district link circuit over conductor 201, contact 230to ground at the intermediate upper contact of relay 209. Relay 117 thenreleases in turn releasing relay 123 whereupon the calling line isdisconnected from the windings of realy 204. Relay 204 then releases inturn releasing relays 205 and 206.v Following the release of relay 206the trunk circuit and all apparatus which has been taken into usethereby is released.

Relay 123 upon releasing now connects the calling line as previouslydescribed to the windings of relay 126 which thereupon energizes. If thecalling subscriber does not now restore his receiver within thirtyseconds, the thermostatic relay 112 operates over the lower frontcontact of relay 126, the normal terminal and wiper 137 of markingswitch 140, the back contact of relay 134, a back contact of relay 118to off-normal ground on conductor 138. As'previously described, relay112 causes the o eration of the calling line fault relay 159 w ichsignals the attendant and causes the release of the district linkcircuit.

If the calling subscriber terminates the conversation prior to thecompletion of the tvelve minute period, the restoration of his receiverreleases relay 204 followed by the release of relays 205 and 206 and therestoration of the remaining equipment employed in the connection. If,however, the calling subscribed holds the connection after the calledsubscriber hangs up, for a period of thirty seconds, a circuit isestablished for the thermostatic relay 217 extending over the lower backcontact of relay 212, which releases when the called subscriber hangsup, thence to ground at the lower front contact of relay 220. After theexpiration of thirty seconds, relay 217 closes its lower contact therebyconnecting direct ground to conductor 201 for shunting down relay 117.The forced release of the connection is then caused in the mannerpreviously described. Similarly after the out-pulsing loop over trunkconductors 207 and 208 is established by relay 204, if pulsing does notbegin the circuit of relay 217 is established over the upper backcontact of relay 211 and the inner upper front contact of relay 210 fora suflicient interval to to cause relay 217 to start the .forced releaseof the established connection.

In the preceding description it was assumed that both meter controlrelays 213 and 214 were operated and that thus for each unit period ofconversation five metering impulses were transmitted by switch 200 foroperating the calling line message register magnet. Had meter controlrelay 214 been operated alone it is obvious that but three meteringimpulses would have been trans-.

mitted and that similarly had relay 213 been operated alone but twometering impulses would have been transmitted.

If a community oifice of an exchange system has less than one hundredlines a link circuit of the type shown in Fig. 4 may be used in place ofthe link circuit of Fig. 1. Calling lines have access to this linkcircuit in the same manner as described in connection with Fig. 1 andthe link circuit has access to outgoing trunks and register circuits themanner previously described thereby closing a start circuit for the linefinder 1400 extending from battery, over the windingand interruptercontacts of stepping magnet 406, the lower back contact of relay 409,

contacts of relay 105 to ground at the back contact of relay 408. Whenthe test wiper 411 of the line finder engages the test terminal of thecalling line, battery potential is encountered and an operating circuitis established over the normal contact of thermostat1c relay 412,winding of test relay 408, contacts of test ack 407, normal terminal and-wiper 401 of the tens marking switch 430,

normal contacts of off -normal switches 402 and 403 in parallel of groupselectors 410 and 420, inner lower normal contacts of relay 413 toground atthe upper normal contacts of relay 409. Relay 408 then operatesand opens the clrcuit of magnet 406 and closes an 'obvious circuit forrelay 413.

With relay 413 operateddirect ground is connected to wiper 411 throughthe winding of relay 408, the inner lower front contact of relay 413 andthe upper normal contacts of relay 409 to prevent the seizure of thecalling line by another line finder, and a circuit is closed forstepping magnet 414 of the group selector 410 to advance the groupselector to hunt for an idle outgoing trunk. This circuit extends frombattery, through the winding and interrupter c'ontacts of magnet 414,wiper 404 and the strapped terminals of the upper half of the bank withwhich 1t is associated, the back contact of test relay 417 to ground atthe lower front contact of relay 413. When an idle trunk is found relay417 operates in a circuit extending from battery on the test-terminal ofthe idle trunk,

wiper 422, the upper front. contact of relay 413, winding of relay 417,wiper 421 and strapped terminals of the marking level of group selector410 to ground over wiper 419 of the marking switch.

.Relay 417 now opens the circuit of magnet 414 to arrest the operationof the group selector 410 and establishes a circuit for relay 423extending from battery, through the winding of this relay, the normalterminal and wiper 405 of the marking switch, front contact of relay 417to ground at the lower front contact of relay 413. At its inner lowerfront contact relay 423 closes an obvious circuit for relay 424. Relay424 upon operating establishes a circuit from ground, through thewinding of relay 409, over wiper 425 of the line finder 400 to batterythrough the cut-off relay 103 of the calling line. Relay 103 disconnectsthe line relay 102 which in turn releases relay 408 and if there are atthe time no other lines calling in' the group the start relay 105 isalso released thereby arresting the operation of other line finders thatmay have been started. After the release of relay 408 relay 413 islocked over its inner upper front contact, the upper back contact ofrelay 426 to ground over conductor 438 and the inner upper front contactof relay 409.

With the relays 409 and 423 operated the calling line is extended overwipers 428 and 429 of line finder 400 and wipers 427 and 431 of groupselector 410 to the selected trunk circuit. The trunk'circuit of Fig. 2then functions in the manner previously described to connect itself withan idle registering device such as is disclosed in Fig. 3. In responseto the dialing of the first three digits of the wantedd-ine number,which will be assumed to be 7 4325 indicative of a local subscribersline terminating in the bank of group selector 410, the registeringdevice registers these digits and as previously described, causes theoperation of relay 215 in the trunk circuit.

The operation of' relay 215 -nowcauses the release of test relay 417 inthe link circuit followed by the release of relay 423 and also causesthe release of all apparatus associated with the trunk circuit and therelease of the registering device.

At the district link circuit of Fig. 4 upon the release of relay 423 thewindings of relay 426 are connected to the calling line loop over thecontacts of relay 409 before the slow to release relay 424 has timetorelease following the release of relay 423, and a new holding circuitfor relay 424 is therefore established over the upper front contact ofrelay 426 to ground on conductor 438. l/Vhen the calling subscriber nowdials the tens digit which was assumed to be 2, relay 426 releases foreach dial impulse and establishes a circuit for the marking switchmagnet 432 which extends from battery, through the winding of magnet432, the upper normal contact of relay 415, winding of slow to releaserelay 434, inner upper back contact of relay 413, which released uponthe operation of relay 426, back contact of relay 426 to ground onconductor 438. Slow to release relay 434 operates in series with magnet432 and remains operated until the tens series of impulses isterminated. When the marking switch leaves normal a circuit is closedfor advancing the group selector 410 which may be traced from battery,through the winding and interrupter contacts of magnet 414, wiper 404,back contact of relay 417, off-normal terminals and wiper 416, lowernormal contacts of relay 415 to ground on conductor438. When the tensdigit impulses terminate and the test wiper 421 reaches terminal 442marked by wiper 419 of the marking switch a circuit is completed forrelay 417 extending from ground on wiper 419, terminal 442, wiper 421winding of relay 417 to battery at the upper back contact of relay 413.

With relay 417 operated the circuit of magnet 414 is opened to arrestfurther movement of the group selector and a circuit is established forrelay 415 extending from battery through the windings of relay 415,off-normal terminals and wiper 405, front contact of relay 417,off-normal terminals and wiper 416, inner lower normal contacts of relay415 to ground on conductor 438. Relay 415 locks over its windings andinner lower front contact to ground on conductor 438. When the callingsubscriber now dials the units impulses the stepping magnet 414 isoperated directly from the contacts of relay 426 in a circuit extendingfrom battery, through the winding of magnet 414. terminals of the upperhalf of the'bank with which wiper 418 is associated and wiper 418 ofmarking switch 430, upper alternate contacts of relay 415, winding ofrelay 434, inner upper back contact of relay 413, back contact of relay426 to ground on conductor 438. Therefore the wipers of switch 410 arepositioned in response to the dialing of the units digit upon theterminal of the wanted line. Relay 434 operates in this stepping'circuitand establishes a circuit for relay 433 extending from battery, windingof relay 433, inner upper ront contact of relay 415 to ground at thefront contact of relay 434 which in turn establishes an obvious circuitfor relay 436. Relay 436 upon operating locks over the back contactofrelay445 and the lower front contact of relay 436 to ground onconductor 438. When the last units impulse is received relay 434releases followed by the release of slow releasing relay 433.

If the called line is free, test relay 446 energizes before relay 433releases in a circuit extending over test wiper 422, the upper windingof relay 446, the upper front contact of relay 433 to ground at the backcontact of relay 434. Relay 446 operates and locks over its lowerwinding and intermediate lower front contact to ground on conductor 438.The calling subscribers bell is then rung by ringing current applied,from source 452 through the winding of ring cut-off relay 445, the innerlower alternate contacts of relay 436, the inner upper front contacts ofrelay 446, wiper 431 thence through the substation bell, wiper 427, thelower front contact of relay 446, the lowermost front contact of re lay436 to ground on conductor 438 and upon the response of the calledsubscriber relay 445 operates releasing relay 436 to disconnect theringing current source 452. Back bridge relay 454 thereupon o eratesover the called line and the calling line messageregister is operated inthe same manner previously describedin connection with Fig. 1.

Upon the termination'of the conversation the calling subscriber restoreshis receiver to the switchhook releasing relay 426 which in turnreleases relays 424 and 409. Relay 409 in turn removes ground fromconductor 438 releasing relays 415 and 446. 'A restor ing circuit is noweffective for returning the group selector 410 to normal which may betraced from battery, through the winding and interrupter contacts ofmagnet 414, offnormal switch 402, lower normal contacts of relay 413 toground at the upper normal contacts of relay 409. When the groupselector .reaches normal the circuit of magnet 414 is opened at contacts402 and a circuit is closed for returning the marking switch 430 tonormal extending from battery, through the winding and interruptercontacts of magnet 432, off normal terminals and wiper 401, oil-normalcontacts 402, thence to ground at the upper normal contacts ofrelay'409.

It will be noted that if the tens digit of the wanted local subscribersnumber is less than five, the group selector 410 will be employed tocomplete the connection just described. If, however, in response to theimpulses of the tens digit the marking switch advances more than fivesteps, the stepping circuit previously traced for stepping magnet 414 isopened when .wiper 404 leaves its fifth terminal and the furthermovement of the group selector 410 is arrested and the stepping circuitof group selector 420 is made effective over the lower half of the bankof terminals to which wiper 404 has access. This group selector thenadvances to the group terminal marked by the wiper 419. When the groupselection is completed and relay 415 operates as previously describedthe group selector 420 is then set directly upon the terminal of thewanted line by the impulses ofthe units digit by a circuit extendingover the lower half of the bank of terminals to which wiper 418 hasaccess. The circuits then function as previously described except thatwhen the calhng subscriber hangs up the restoring circuit previouslytraced from ground at the upper normal contacts of relay 409,,over thelower normal contacts of relay 413 extends in parallel through the oil'-normal switch contacts 402 and 403 for re storing both group selectorsto normal.

In the event that either subscriber engaged in a local connection over alink circuit of the character disclosed in either Fig. 1 or Fig. 4 isdesired for a toll connection, the toll operator upon connection withmultiples of either line may apply direct ground to the winding ofeither relay 109 or relay 409 thereby releasing the link circuit andreleasing the local connection. 30

What is claimed is:

1. A telephone exchange system comprising a link circuit-terminating atone end in a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the banks of all ofsaid switches, a calling line, means for associating said calling linewith said link circuit, means responsive to such association foroperating one of said switches to select an idle trunk circuit, meansassociable with said selected trunk circuit for registering certaindigits of a wanted line number. means in said link circuit responsive toother digits of a wanted line number for causing the operation of one ofsaid switches to connect with a wanted line, and means controlled bysaid registering means to render said latter means efi'ective only ifsaid certain digits indicate that the connection is to be terminatedlocally.

2. A telephone exchange system comprising a link circuit terminating atoneend in a plurality of parallelly connected selector switches. a groupof outgoing trunk circuits terminating in the terminal bank. of one ofsaid switches, subscribers lines terminating in the remaining terminalsof the banks of said switches, a calling line, means for associatingsaid calling line with said link circuit, means responsive to suchassociation for operating one of said switches to select an idle trunkcircuit, means associable with said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if said certain -digits registered thereinindicate that the call is to be terminated locally for advancing saidone switch to release said trunk, and means"'in said link circuit forthen operating one of said switches in response to the dialing ot' theremaining digits of the wanted line number to extend the calling linetoone of said other subscribers lines.

3. A telephone exchange system comprising a link circuit terminating atone end in a plurality of parallelly connected selector switches. agroup of outgoing trunk circuits terminating in the terminal bank of'oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line, means forassociating said calling line with said link circuit, means responsiveto such association for operating one of said switches to select an idletrunk circuit, means associable when said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if said certain digits registered thereinindicate that the call is to be terminated locally for transmitting asignal back to said link circuit, means responsive to said signal forreleasing said trunk circuit, and means for rendering a particular oneof said switches responsive to further digits dialed by the callingsubscriber for selecting one of said other subscribers lines.

4. A telephone exchange system comprising a link circuit terminating atone end in a' plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks .of said switches, a calling line, means forassociating said calling line with said link circuit, means responsiveto such association for operating one of. saidswitches to select an idletrunk circuit, means associable with said selected trunk circuit forregistering certain digits of a Wanted line number, means controlled bysaid registering means if said certain digits registered indicate thatthe call is to be terminated locally for transmitting discriminatingsignals back to said link circuit, and means responsive to said signalsfor releasing said trunk circuit and for selecting a particular one ofsaid switches for response to further digits dialed by the callingsubscriber for selecting one of said other subscribers lines.

5. A telephone exchange system comprising a link circuit terminating atone end in a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches. subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line. means for associating said calling line with said link circuit, means responsive tosuch association for operating one of said switches to select an idletrunk circuit. means associable with said selected trunk circuit forregistering certain digits of a wanted line number. means controlled bysaid registering means if said certain digits registered indicate thatthe call is to be terminated locally for transmitting discriminatingsignals in accordance with the registered digits back to said linkircuit. means responsive to said signals for releasing said trunkcircuit and for selecting that one of said switches which has access tothe group of subscribers lines in which the wanted line is located, andmeans responsive to the dialing of further digits for setting theselected switch upon the terminals of the wanted line.

6. A telephone exchange system comprising a link circuit terminating atone end in a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line, means forassociating said calling line with said link circuit, means responsiveto such association for operating one of said switches to select an idletrunk circuit, means associable with said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if said certain digits registered indicate thatthe call is to be terminated locally for transmitting discriminatingsignals varying in potential in accordance with the registered digitsback to said link circuit. means responsive to said signals forreleasing said trunk circuit and for selecting that one of said switcheswhich has access to the group of subscribers lines in which the wantedline is located, and means responsive to the dialing of further digitsfor setting the selected switch upon the terminals of the wanted line.

7. A telephone exchange system comprising a trunk circuit terminating atone end in a plurality of parallelly connected selector switches. agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line. means forassociating said calling line with said link circuit, means responsiveto such association for operating one of said switches to select an idletrunk circuit, means associable with said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if said certain digits registered indicate thatthe call is to be terminated locally over that switch which has accessto said trunk circuits for releasing said trunk circuit and forrendering said switch responsive to the dialing of further digits forselecting a wanted subscribers line terminating therein.

8. A telephone exchange system comprising a link circuit terminating atone end in a plurality of parallelly connected selector switches. agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line, means forassociating said calling line with said link circuit, and meansresponsive to such association for operating'said one ofsaid switches toselect an idle outgoing trunk circuit.

9. A telephone exchange system comprising a link circuit terminating atone end in a plurality of parallellyconnected selector switches, a groupof outgoing trunk circuits terminating in the terminal bank of one ofsaid switches, subscribers linesterminating in the remaining terminalsof the banks of said switches, a calling line, means for associatingsaid calling line with said link cir-. cuit, means responsive to suchassociation for operating said one of said switches to select an idleoutgoing trunk circuit, means for registering dialed digits, and meanscontrolled by said registering means for releasing the selected trunkcircuit and for setting one of said switches to select a desired one ofsaid subscribers lines.

10. A. telephone exchange system comprising a link circuit terminatingat one end in a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line, means forassociating said calling line with said link circuit, means responsiveto such association for operating said oneof said switches to select anidle outgoing trunk circuit, means for registering dialed digits, andmeans controlled by said registering means for releasing the selectedtrunk circuit and for either resetting said one switch or for settingone of said other switches to select a desired one of said subscriberslines.

11. A telephone exchange system comprising a link circuit terminating atone end in a plurality of permanently paralleled selector switches,-acalling line, means for associating said line with said link circuit.trunk circuits and subscribers lines terminating in the bank of one ofsaid switches, subscribers lines terminating in the bank of the other ofsaid switches, and means controlled over said calling line for operatingsaid switches to connect with a trunk circuit or with a desired one ofsaid subscribers lines.

12. A. telephone exchange system comprising a link circuit terminatingat one end in a plurality of permanently paralleled selector switches, acalling line, means for associating ing a link circuit terminating atone end in a selector switch, a calling line, means for associating saidline withsaidclink circuit, subscribers lines terminating in the bank ofsaid selector switch, means controlled over said calling line forextending a conversational connection over said selector switch to adesired line, and thermostatic means operative to restore theestablished connection a predetermined interval after the calledsubscriber has restored his receiver if said calling subscriber has notrestored his receiver.

14. A telephone exchange system comprising a link circuit terminating atone end in a plurality of permanently paralleled selector switches, acalling line, means for-associating said line with said link circuit,subscribers lines terminating in the banks of-said selector switches,means controlled over said calling line for operating said switches toextend a conversational connection with a desired one .of saidsubscribers lines, and means operative a predetermined interval afterthe called subscriber has restored his receiver if the callingsubscriber has not restored his receiver. for releasing the extendedconnection.

15. A telephone exchange system comprising a link circuit terminatingatone end in a selector switch, a calling line, means for associatingsaid line with said link circuit, trunk circuits terminating in the bankof said selector switch, means responsive to the association of saidline with said link circuit for operating said selector switch to selectan idle trunk circuit, means in said trunk circuit responsive to theresponse of a called subscriber connected thereover and means in saidtrunk circuit operative a predetermined interval after the calledsubscriber has restored his receiver if the calling subscriber has notrestored his receiver for releasing the connection.

16. A telephone system comprising a link circuit terminatingin aplurality of permanently paralleled selector switches, a calling line,means for associating said line with said link circuit, subscriberslines terminating in the bank of one of said switches, subscribers linesterminating in the bank of the other of said switches, a marking switchcontrollable by said calling line to direct the setting of any one ofsaid switches in a first selection movement, and means for furthersetting such switch in a further selection movement directly under thecontrol of said calling line.

17. A telephone exchange system comprising a link circuit terminating atone end in. a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line,-means forassociating said calling line with said link circuit, means responsiveto such associaton for opcrating one of said switches to select an idletrunk circuit, means associable with said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if certain digits registered therein indicatethat the call is to be terminated locally for advancing said one switchto release said trunk, a marking switch in said link circuit operable inaccordance with a further digit dialed by said calling subscriber fordirecting one of said selector switches in aline group selectionmovement, and means operative in response to a further dialed digit todirectly set said selector to select the terminals of a desiredsubscribers line.

18. A telephone exchange system comprising a link circuit terminating'atone end in a plurality of parallelly connected selector switches, agroup of outgoing trunk circuits terminating in the terminal bank of oneof said switches, subscribers lines terminating in the remainingterminals of the banks of said switches, a calling line, means forassociating said calling line with said link circuit, means responsiveto such association for operating one of said switches to select an idletrunk circuit, means associable with said selected trunk circuit forregistering certain digits of a wanted line number, means controlled bysaid registering means if certain digits registered therein indicatethat the call is to be tern'linated locally for transmittingdiscriminating signals back to said link circuit, means responsive tosaid signals for releasing said trunk circuit and for selecting aparticular one of said switches for response to further digits dialed bythe calling subscriber, a marking switch in said link circuit operablein accordance with one of said further digits dialed for directing theselector switch in a line group selection movement, and means operablein response to a further one of said digits to directly set suchselector to select the terminals of a desired subscrib-.

ers line.

In witness whereof we hereunto subscribe our names this 19th day ofFebruary, 1930. WILLIAM. HATTON. CHARLES DE VRIENDT. ERNEST JEANROUSSEAU.

